The commit: 3f235279828c ("x86/cpu: Restore AMD's DE_CFG MSR after resume")
which was backported from the upstream commit: 2632daebafd0 renamed the
MSR_F10H_DECFG_LFENCE_SERIALIZE macro to MSR_AMD64_DE_CFG_LFENCE_SERIALIZE.
The fix for 4.14 and 4.9 changed MSR_F10H_DECFG_LFENCE_SERIALIZE to
MSR_AMD64_DE_CFG_LFENCE_SERIALIZE_BIT in the init_amd() function, but
should have used MSR_AMD64_DE_CFG_LFENCE_SERIALIZE.
This causes a discrepency in the LFENCE serialization check in the
init_amd() function.
This causes a ~16% sysbench memory regression, when running:
sysbench --test=memory run
Fixes: 3f235279828c ("x86/cpu: Restore AMD's DE_CFG MSR after resume")
Signed-off-by: Rhythm Mahajan <rhythm.m.mahajan@xxxxxxxxxx>
---
v1->v2
Corrected the formatting of the commit message.
---
The test result before the commit 3f235279828c ("x86/cpu: Restore AMD's DE_CFG MSR after resume")
$ sysbench --test=memory run
sysbench 1.0.17 (using system LuaJIT 2.0.4)
Running the test with following options:
Number of threads: 1
Initializing random number generator from current time
Running memory speed test with the following options:
block size: 1KiB
total size: 102400MiB
operation: write
scope: global
Initializing worker threads...
Threads started!
Total operations: 27466829 (2746182.07 per second)
26823.08 MiB transferred (2681.82 MiB/sec)
General statistics:
total time: 10.0001s
total number of events: 27466829
Latency (ms):
min: 0.00
avg: 0.00
max: 0.20
95th percentile: 0.00
sum: 4041.60
Threads fairness:
events (avg/stddev): 27466829.0000/0.00
execution time (avg/stddev): 4.0416/0.00
The test result after the commit 3f235279828c ("x86/cpu: Restore AMD's DE_CFG MSR after resume")
$ sysbench --test=memory run
sysbench 1.0.17 (using system LuaJIT 2.0.4)
Running the test with following options:
Number of threads: 1
Initializing random number generator from current time
Running memory speed test with the following options:
block size: 1KiB
total size: 102400MiB
operation: write
scope: global
Initializing worker threads...
Threads started!
Total operations: 33758407 (3375232.84 per second)
32967.19 MiB transferred (3296.13 MiB/sec)
General statistics:
total time: 10.0001s
total number of events: 33758407
Latency (ms):
min: 0.00
avg: 0.00
max: 0.06
95th percentile: 0.00
sum: 4115.95
Threads fairness:
events (avg/stddev): 33758407.0000/0.00
execution time (avg/stddev): 4.1160/0.00
---
arch/x86/kernel/cpu/amd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index ee5d0f943ec8..4122afeaaaff 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -941,7 +941,7 @@ static void init_amd(struct cpuinfo_x86 *c)
* serializing.
*/
ret = rdmsrl_safe(MSR_AMD64_DE_CFG, &val);
- if (!ret && (val & MSR_AMD64_DE_CFG_LFENCE_SERIALIZE_BIT)) {
+ if (!ret && (val & MSR_AMD64_DE_CFG_LFENCE_SERIALIZE)) {
/* A serializing LFENCE stops RDTSC speculation */
set_cpu_cap(c, X86_FEATURE_LFENCE_RDTSC);
} else {
--
2.39.2
